1. Field of the Invention
The present invention generally relates to keyboard structures used in electronic apparatus and, in a preferred embodiment thereof, more particularly relates to a specially designed liquid spill-sensing keyboard assembly operatively incorporated in a notebook computer.
2. Description of Related Art
During use of a portable notebook computer resting atop a desk or other horizontal support surface (such as an airplane seat tray), the keyboard portion of the computer is susceptible to having a drink liquid (such as coffee, water or a soft drink) spilled on it by it by the computer user. If some measure is not taken to prevent the spilled liquid from flowing from the keyboard onto to the underlying major internal electrical components of the computer (such as the circuit boards, drives and the like) these components, commonly referred to as the xe2x80x9csystem electronicsxe2x80x9d can be shorted out by the spilled liquid and severely damaged.
Typically, portable computer keyboard and associated electrical system designs incorporate some means for either (1) sealing off areas of the keyboard/system to prevent the spilled liquid from reaching the underlying system electronics, (2) absorbing and containing the spilled liquid, or (3) diverting the spilled liquid from the keyboard to a safe place in the computer where it will not short out the system electronics therein.
For example, where a liquid sealing technique is employed the keyboard installs into an opening in the portable computer with a rubber/plastic gasket which is designed to prevent liquid spills on the top surface of the keyboard from draining therefrom into the interior of the computer. In the absorption approach the bottom or perimeter of the keyboard is equipped with an absorbing material (functioning as a xe2x80x9cdiaperxe2x80x9d) which absorbs and retains the liquid spilled on the top side of the keyboard. When the diverting approach is used the liquid is allowed to pass through or around the keyboard, via built-in xe2x80x9cchannelingxe2x80x9d passages, in specific areas to drain the liquid into a location isolated from the computer system electronics underlying the keyboard.
Ensuring a tight liquid keyboard seal in a computer production environment is difficult, and absorbing or diverting liquids spilled on the keyboard undesirably adds extra cost and space requirements for these features. In view of this it can readily be seen that a need exists for apparatus that protects the computer system electronics from short circuit damage arising from a spillage of liquid on the keyboard in a manner avoiding or at least substantially reducing the above-mentioned problems, limitations and disadvantages typically associated with conventional liquid spillage sealing, absorbing and diverting techniques applied to portable computer keyboards.
In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, an electronic apparatus, representatively a portable computer notebook computer, is provided with a specially designed liquid spill sensing keyboard which is operative to sense the presence of liquid spilled on the keyboard and responsively shut down the computer""s system electronics before they can be contacted, shorted out and damaged by the spilled liquid.
The keyboard is carried on the top side of the base housing portion of the portable computer and is preferably provided with electrical liquid spill detection circuitry having a portion positioned and configured to be contacted and shorted out by liquid spilled on the keyboard. In response, the shorted out detection circuitry creates a liquid spill detection signal which is used to shut down the system electronics. Illustratively, the detection circuitry portion positioned to be contacted and shorted out by the spilled liquid includes a spaced plurality of electrically interconnected normally open switch structures incorporated in a multi-laver signal pad portion of the keyboard which underlies the depressible keys thereof and is interposed between the keys and the underlying system electronics in the base housing of the computer.
In a preferred embodiment of the keyboard, the multi-layer signal pad has a top layer, a second layer disposed beneath the top layer and having a top side facing the top layer, and a spaced series of openings extending downwardly through the top layer to portions of the second layer top side, and fluid tight seal structures laterally circumscribing the openings. The normally open switch structures are carried on the top side portions of the second layer, exposed at the bottom ends of the pad openings, and are operative to be contacted and shorted out by liquid entering the openings.
The detection circuitry incorporated in the multi-layer signal pad is representatively coupled to a keyboard controller, and a system controller is operatively interconnected between the keyboard controller and a power supply portion of the system electronics. When liquid spilled on the keyboard passes through openings in the support structure which carries the depressible key members it enters at least one of the top side signal pad openings and shorts out the associated normally open detection switch structure(s). The spilled liquid signal is responsively transmitted from the keyboard controller to the system controller which, in turn, transmits a shut-down signal to the power supply portion of the system electronics, thereby shutting off the computer before its system electronics can be contacted, shorted out and damaged by the spilled liquid.